/**
 * Cesium - https://github.com/AnalyticalGraphicsInc/cesium
 *
 * Copyright 2011-2017 Cesium Contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Columbus View (Pat. Pend.)
 *
 * Portions licensed separately.
 * See https://github.com/AnalyticalGraphicsInc/cesium/blob/master/LICENSE.md for full licensing details.
 */
define(['./when-8d13db60', './Check-70bec281', './Math-61ede240', './Cartographic-fe4be337', './Cartesian2-85064f09', './BoundingSphere-775c5788', './Cartesian4-5af5bb24', './RuntimeError-ba10bc3e', './WebGLConstants-4c11ee5f', './ComponentDatatype-5862616f', './FeatureDetection-7bd32c34', './Transforms-b2e71640', './buildModuleUrl-14bfe498', './AttributeCompression-84a90a13', './IndexDatatype-9435b55f', './IntersectionTests-397d9494', './Plane-8390418f', './WebMercatorProjection-80c70558', './createTaskProcessorWorker', './EllipsoidTangentPlane-a815c96f', './OrientedBoundingBox-635e6e10', './TerrainEncoding-a807a704'], function (when, Check, _Math, Cartographic, Cartesian2, BoundingSphere, Cartesian4, RuntimeError, WebGLConstants, ComponentDatatype, FeatureDetection, Transforms, buildModuleUrl, AttributeCompression, IndexDatatype, IntersectionTests, Plane, WebMercatorProjection, createTaskProcessorWorker, EllipsoidTangentPlane, OrientedBoundingBox, TerrainEncoding) { 'use strict';

    /**
         * Provides terrain or other geometry for the surface of an ellipsoid.  The surface geometry is
         * organized into a pyramid of tiles according to a {@link TilingScheme}.  This type describes an
         * interface and is not intended to be instantiated directly.
         *
         * @alias TerrainProvider
         * @constructor
         *
         * @see EllipsoidTerrainProvider
         * @see CesiumTerrainProvider
         * @see VRTheWorldTerrainProvider
         * @see GoogleEarthEnterpriseTerrainProvider
         */
        function TerrainProvider() {
            Check.DeveloperError.throwInstantiationError();
        }

        Object.defineProperties(TerrainProvider.prototype, {
            /**
             * Gets an event that is raised when the terrain provider encounters an asynchronous error..  By subscribing
             * to the event, you will be notified of the error and can potentially recover from it.  Event listeners
             * are passed an instance of {@link TileProviderError}.
             * @memberof TerrainProvider.prototype
             * @type {Event}
             */
            errorEvent : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets the credit to display when this terrain provider is active.  Typically this is used to credit
             * the source of the terrain. This function should
             * not be called before {@link TerrainProvider#ready} returns true.
             * @memberof TerrainProvider.prototype
             * @type {Credit}
             */
            credit : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets the tiling scheme used by the provider.  This function should
             * not be called before {@link TerrainProvider#ready} returns true.
             * @memberof TerrainProvider.prototype
             * @type {TilingScheme}
             */
            tilingScheme : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets a value indicating whether or not the provider is ready for use.
             * @memberof TerrainProvider.prototype
             * @type {Boolean}
             */
            ready : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets a promise that resolves to true when the provider is ready for use.
             * @memberof TerrainProvider.prototype
             * @type {Promise.<Boolean>}
             * @readonly
             */
            readyPromise : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets a value indicating whether or not the provider includes a water mask.  The water mask
             * indicates which areas of the globe are water rather than land, so they can be rendered
             * as a reflective surface with animated waves.  This function should not be
             * called before {@link TerrainProvider#ready} returns true.
             * @memberof TerrainProvider.prototype
             * @type {Boolean}
             */
            hasWaterMask : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets a value indicating whether or not the requested tiles include vertex normals.
             * This function should not be called before {@link TerrainProvider#ready} returns true.
             * @memberof TerrainProvider.prototype
             * @type {Boolean}
             */
            hasVertexNormals : {
                get : Check.DeveloperError.throwInstantiationError
            },

            /**
             * Gets an object that can be used to determine availability of terrain from this provider, such as
             * at points and in rectangles.  This function should not be called before
             * {@link TerrainProvider#ready} returns true.  This property may be undefined if availability
             * information is not available.
             * @memberof TerrainProvider.prototype
             * @type {TileAvailability}
             */
            availability : {
                get : Check.DeveloperError.throwInstantiationError
            }
        });

        var regularGridIndicesCache = [];

        /**
         * Gets a list of indices for a triangle mesh representing a regular grid.  Calling
         * this function multiple times with the same grid width and height returns the
         * same list of indices.  The total number of vertices must be less than or equal
         * to 65536.
         *
         * @param {Number} width The number of vertices in the regular grid in the horizontal direction.
         * @param {Number} height The number of vertices in the regular grid in the vertical direction.
         * @returns {Uint16Array|Uint32Array} The list of indices. Uint16Array gets returned for 64KB or less and Uint32Array for 4GB or less.
         */
        TerrainProvider.getRegularGridIndices = function(width, height) {
            //>>includeStart('debug', pragmas.debug);
            if (width * height >= _Math.CesiumMath.FOUR_GIGABYTES) {
                throw new Check.DeveloperError('The total number of vertices (width * height) must be less than 4,294,967,296.');
            }
            //>>includeEnd('debug');

            var byWidth = regularGridIndicesCache[width];
            if (!when.defined(byWidth)) {
                regularGridIndicesCache[width] = byWidth = [];
            }

            var indices = byWidth[height];
            if (!when.defined(indices)) {
                if (width * height < _Math.CesiumMath.SIXTY_FOUR_KILOBYTES) {
                    indices = byWidth[height] = new Uint16Array((width - 1) * (height - 1) * 6 + 3*(width + height - 2));
                } else {
                    indices = byWidth[height] = new Uint32Array((width - 1) * (height - 1) * 6 + 3*(width + height - 2));
                }
                addRegularGridIndices(width, height, indices, 0);
            }

            return indices;
        };

        TerrainProvider.getRegularGridIndicesForReproject = function(width, height) {
            //>>includeStart('debug', pragmas.debug);
            if (width * height >= _Math.CesiumMath.FOUR_GIGABYTES) {
                throw new Check.DeveloperError('The total number of vertices (width * height) must be less than 4,294,967,296.');
            }
            //>>includeEnd('debug');

            var byWidth = regularGridIndicesCache[width];
            if (!when.defined(byWidth)) {
                regularGridIndicesCache[width] = byWidth = [];
            }

            var indices = byWidth[height];
            if (!when.defined(indices)) {
                if (width * height < _Math.CesiumMath.SIXTY_FOUR_KILOBYTES) {
                    indices = byWidth[height] = new Uint16Array((width - 1) * (height - 1) * 6);
                } else {
                    indices = byWidth[height] = new Uint32Array((width - 1) * (height - 1) * 6);
                }
                addRegularGridIndices(width, height, indices, 0);
            }

            return indices;
        };

        var regularGridAndEdgeIndicesCache = [];

        /**
         * @private
         */
        TerrainProvider.getRegularGridIndicesAndEdgeIndices = function(width, height) {
            //>>includeStart('debug', pragmas.debug);
            if (width * height >= _Math.CesiumMath.FOUR_GIGABYTES) {
                throw new Check.DeveloperError('The total number of vertices (width * height) must be less than 4,294,967,296.');
            }
            //>>includeEnd('debug');

            var byWidth = regularGridAndEdgeIndicesCache[width];
            if (!when.defined(byWidth)) {
                regularGridAndEdgeIndicesCache[width] = byWidth = [];
            }

            var indicesAndEdges = byWidth[height];
            if (!when.defined(indicesAndEdges)) {
                var indices = TerrainProvider.getRegularGridIndices(width, height);

                var edgeIndices = getEdgeIndices(width, height);
                var westIndicesSouthToNorth = edgeIndices.westIndicesSouthToNorth;
                var southIndicesEastToWest = edgeIndices.southIndicesEastToWest;
                var eastIndicesNorthToSouth = edgeIndices.eastIndicesNorthToSouth;
                var northIndicesWestToEast = edgeIndices.northIndicesWestToEast;

                indicesAndEdges = byWidth[height] = {
                    indices : indices,
                    westIndicesSouthToNorth : westIndicesSouthToNorth,
                    southIndicesEastToWest : southIndicesEastToWest,
                    eastIndicesNorthToSouth : eastIndicesNorthToSouth,
                    northIndicesWestToEast : northIndicesWestToEast
                };
            }

            return indicesAndEdges;
        };

        var regularGridAndSkirtAndEdgeIndicesCache = [];

        /**
         * @private
         */
        TerrainProvider.getRegularGridAndSkirtIndicesAndEdgeIndices = function(width, height) {
            //>>includeStart('debug', pragmas.debug);
            if (width * height >= _Math.CesiumMath.FOUR_GIGABYTES) {
                throw new Check.DeveloperError('The total number of vertices (width * height) must be less than 4,294,967,296.');
            }
            //>>includeEnd('debug');

            var byWidth = regularGridAndSkirtAndEdgeIndicesCache[width];
            if (!when.defined(byWidth)) {
                regularGridAndSkirtAndEdgeIndicesCache[width] = byWidth = [];
            }

            var indicesAndEdges = byWidth[height];
            if (!when.defined(indicesAndEdges)) {
                var gridVertexCount = width * height;
                var gridIndexCount = (width - 1) * (height - 1) * 6;
                var edgeVertexCount = width * 2 + height * 2;
                var edgeIndexCount = Math.max(0, edgeVertexCount - 4) * 6;
                var vertexCount = gridVertexCount + edgeVertexCount;

                var boundaryIndexCount = 3*(width + height - 2);

                var indexCount = gridIndexCount + edgeIndexCount + boundaryIndexCount;

                var edgeIndices = getEdgeIndices(width, height);
                var westIndicesSouthToNorth = edgeIndices.westIndicesSouthToNorth;
                var southIndicesEastToWest = edgeIndices.southIndicesEastToWest;
                var eastIndicesNorthToSouth = edgeIndices.eastIndicesNorthToSouth;
                var northIndicesWestToEast = edgeIndices.northIndicesWestToEast;

                var indices = IndexDatatype.IndexDatatype.createTypedArray(vertexCount, indexCount);
                addRegularGridIndices(width, height, indices, 0);
                TerrainProvider.addSkirtIndices(westIndicesSouthToNorth, southIndicesEastToWest, eastIndicesNorthToSouth, northIndicesWestToEast, gridVertexCount, indices, gridIndexCount + boundaryIndexCount);

                indicesAndEdges = byWidth[height] = {
                    indices : indices,
                    westIndicesSouthToNorth : westIndicesSouthToNorth,
                    southIndicesEastToWest : southIndicesEastToWest,
                    eastIndicesNorthToSouth : eastIndicesNorthToSouth,
                    northIndicesWestToEast : northIndicesWestToEast,
                    indexCountWithoutSkirts : gridIndexCount
                };
            }

            return indicesAndEdges;
        };

        /**
         * @private
         */
        TerrainProvider.addSkirtIndices = function(westIndicesSouthToNorth, southIndicesEastToWest, eastIndicesNorthToSouth, northIndicesWestToEast, vertexCount, indices, offset, edgeMap) {
            var vertexIndex = vertexCount;
            offset = addSkirtIndices(westIndicesSouthToNorth, vertexIndex, indices, offset, edgeMap);
            vertexIndex += westIndicesSouthToNorth.length;
            offset = addSkirtIndices(southIndicesEastToWest, vertexIndex, indices, offset, edgeMap);
            vertexIndex += southIndicesEastToWest.length;
            offset = addSkirtIndices(eastIndicesNorthToSouth, vertexIndex, indices, offset, edgeMap);
            vertexIndex += eastIndicesNorthToSouth.length;
            addSkirtIndices(northIndicesWestToEast, vertexIndex, indices, offset, edgeMap);
        };

        function getEdgeIndices(width, height) {
            var westIndicesSouthToNorth = new Array(height);
            var southIndicesEastToWest = new Array(width);
            var eastIndicesNorthToSouth = new Array(height);
            var northIndicesWestToEast = new Array(width);

            var i;
            for (i = 0; i < width; ++i) {
                northIndicesWestToEast[i] = i;
                southIndicesEastToWest[i] = width * height - 1 - i;
            }

            for (i = 0; i < height; ++i) {
                eastIndicesNorthToSouth[i] = (i + 1) * width - 1;
                westIndicesSouthToNorth[i] = (height - i - 1) * width;
            }

            return {
                westIndicesSouthToNorth : westIndicesSouthToNorth,
                southIndicesEastToWest : southIndicesEastToWest,
                eastIndicesNorthToSouth : eastIndicesNorthToSouth,
                northIndicesWestToEast : northIndicesWestToEast
            };
        }

        function addRegularGridIndices(width, height, indices, offset) {
            var index = 0;
            for (var j = 0; j < height - 1; ++j) {
                for (var i = 0; i < width - 1; ++i) {
                    var upperLeft = index;
                    var lowerLeft = upperLeft + width;
                    var lowerRight = lowerLeft + 1;
                    var upperRight = upperLeft + 1;

                    indices[offset++] = upperLeft;
                    indices[offset++] = lowerLeft;
                    indices[offset++] = upperRight;
                    indices[offset++] = upperRight;
                    indices[offset++] = lowerLeft;
                    indices[offset++] = lowerRight;

                    ++index;
                }
                ++index;
            }
            var boundaryHeight = (height - 1)/2;
            var boundaryWidth = (width - 1)/2;

            index = 0;
            for(var i=0; i<boundaryWidth; i++)
            {
                indices[offset++] = index;
                indices[offset++] = index + 1;
                indices[offset++] = index + 2;
                index+=2;
            }

            index = width * (height - 1);
            for(var i=0; i<boundaryWidth; i++)
            {
                indices[offset++] = index + 1;
                indices[offset++] = index;
                indices[offset++] = index + 2;
                index+=2;
            }

            index = 0;
            for(var i=0; i<boundaryHeight; i++)
            {
                indices[offset++] = index + width;
                indices[offset++] = index;
                indices[offset++] = index + 2*width;
                index+=2*width;
            }

            index = width - 1;
            for(var i=0; i<boundaryHeight; i++)
            {
                indices[offset++] = index;
                indices[offset++] = index + width;
                indices[offset++] = index + 2*width;
                index+=2*width;
            }
        }

        function addSkirtIndices(edgeIndices, vertexIndex, indices, offset, edgeMap) {
            var hasEdgeMap = when.defined(edgeMap);
            var previousIndex = edgeIndices[0];

            var length = edgeIndices.length;
            for (var i = 1; i < length; ++i) {
                var index = edgeIndices[i];

                if(hasEdgeMap && !edgeMap[previousIndex + '_' + index]){
                    continue ;
                }

                indices[offset++] = previousIndex;
                indices[offset++] = index;
                indices[offset++] = vertexIndex;

                indices[offset++] = vertexIndex;
                indices[offset++] = index;
                indices[offset++] = vertexIndex + 1;

                previousIndex = index;
                ++vertexIndex;
            }

            return offset;
        }

        /**
         * Specifies the quality of terrain created from heightmaps.  A value of 1.0 will
         * ensure that adjacent heightmap vertices are separated by no more than
         * {@link Globe.maximumScreenSpaceError} screen pixels and will probably go very slowly.
         * A value of 0.5 will cut the estimated level zero geometric error in half, allowing twice the
         * screen pixels between adjacent heightmap vertices and thus rendering more quickly.
         * @type {Number}
         */
        TerrainProvider.heightmapTerrainQuality = 0.25;

        /**
         * Determines an appropriate geometric error estimate when the geometry comes from a heightmap.
         *
         * @param {Ellipsoid} ellipsoid The ellipsoid to which the terrain is attached.
         * @param {Number} tileImageWidth The width, in pixels, of the heightmap associated with a single tile.
         * @param {Number} numberOfTilesAtLevelZero The number of tiles in the horizontal direction at tile level zero.
         * @returns {Number} An estimated geometric error.
         */
        TerrainProvider.getEstimatedLevelZeroGeometricErrorForAHeightmap = function(ellipsoid, tileImageWidth, numberOfTilesAtLevelZero) {
            return ellipsoid.maximumRadius * 2 * Math.PI * TerrainProvider.heightmapTerrainQuality / (tileImageWidth * numberOfTilesAtLevelZero);
        };

        /**
         * Requests the geometry for a given tile.  This function should not be called before
         * {@link TerrainProvider#ready} returns true.  The result must include terrain data and
         * may optionally include a water mask and an indication of which child tiles are available.
         * @function
         *
         * @param {Number} x The X coordinate of the tile for which to request geometry.
         * @param {Number} y The Y coordinate of the tile for which to request geometry.
         * @param {Number} level The level of the tile for which to request geometry.
         * @param {Request} [request] The request object. Intended for internal use only.
         *
         * @returns {Promise.<TerrainData>|undefined} A promise for the requested geometry.  If this method
         *          returns undefined instead of a promise, it is an indication that too many requests are already
         *          pending and the request will be retried later.
         */
        TerrainProvider.prototype.requestTileGeometry = Check.DeveloperError.throwInstantiationError;

        /**
         * Gets the maximum geometric error allowed in a tile at a given level.  This function should not be
         * called before {@link TerrainProvider#ready} returns true.
         * @function
         *
         * @param {Number} level The tile level for which to get the maximum geometric error.
         * @returns {Number} The maximum geometric error.
         */
        TerrainProvider.prototype.getLevelMaximumGeometricError = Check.DeveloperError.throwInstantiationError;

        /**
         * Determines whether data for a tile is available to be loaded.
         * @function
         *
         * @param {Number} x The X coordinate of the tile for which to request geometry.
         * @param {Number} y The Y coordinate of the tile for which to request geometry.
         * @param {Number} level The level of the tile for which to request geometry.
         * @returns {Boolean} Undefined if not supported by the terrain provider, otherwise true or false.
         */
        TerrainProvider.prototype.getTileDataAvailable = Check.DeveloperError.throwInstantiationError;

        /**
         * Makes sure we load availability data for a tile
         * @function
         *
         * @param {Number} x The X coordinate of the tile for which to request geometry.
         * @param {Number} y The Y coordinate of the tile for which to request geometry.
         * @param {Number} level The level of the tile for which to request geometry.
         * @returns {undefined|Promise} Undefined if nothing need to be loaded or a Promise that resolves when all required tiles are loaded
         */
        TerrainProvider.prototype.loadTileDataAvailability = Check.DeveloperError.throwInstantiationError;

    var maxShort = 32767;

    var cartesian3Scratch = new Cartographic.Cartesian3();
    var scratchMinimum = new Cartographic.Cartesian3();
    var scratchMaximum = new Cartographic.Cartesian3();
    var cartographicScratch = new Cartographic.Cartographic();
    var toPack = new Cartesian2.Cartesian2();
    var scratchNormal = new Cartographic.Cartesian3();
    var scratchToENU = new BoundingSphere.Matrix4();
    var scratchFromENU = new BoundingSphere.Matrix4();

    function createVerticesFromQuantizedTerrainMesh(parameters, transferableObjects) {
        var quantizedVertices = parameters.quantizedVertices;
        var quantizedVertexCount = quantizedVertices.length / 3;
        var octEncodedNormals = parameters.octEncodedNormals;
        var edgeVertexCount = parameters.westIndices.length + parameters.eastIndices.length +
            parameters.southIndices.length + parameters.northIndices.length;
        var includeWebMercatorT = parameters.includeWebMercatorT;

        var rectangle = Cartesian2.Rectangle.clone(parameters.rectangle);
        var west = rectangle.west;
        var south = rectangle.south;
        var east = rectangle.east;
        var north = rectangle.north;

        var ellipsoid = Cartesian2.Ellipsoid.clone(parameters.ellipsoid);

        var exaggeration = parameters.exaggeration;
        var minimumHeight = parameters.minimumHeight * exaggeration;
        var maximumHeight = parameters.maximumHeight * exaggeration;

        var center = parameters.relativeToCenter;
        var fromENU = Transforms.Transforms.eastNorthUpToFixedFrame(center, ellipsoid);
        var toENU = BoundingSphere.Matrix4.inverseTransformation(fromENU, new BoundingSphere.Matrix4());

        var southMercatorY;
        var oneOverMercatorHeight;
        if (includeWebMercatorT) {
            southMercatorY = WebMercatorProjection.WebMercatorProjection.geodeticLatitudeToMercatorAngle(south);
            oneOverMercatorHeight = 1.0 / (WebMercatorProjection.WebMercatorProjection.geodeticLatitudeToMercatorAngle(north) - southMercatorY);
        }

        var uBuffer = quantizedVertices.subarray(0, quantizedVertexCount);
        var vBuffer = quantizedVertices.subarray(quantizedVertexCount, 2 * quantizedVertexCount);
        var heightBuffer = quantizedVertices.subarray(quantizedVertexCount * 2, 3 * quantizedVertexCount);
        var hasVertexNormals = when.defined(octEncodedNormals);

        var uvs = new Array(quantizedVertexCount);
        var heights = new Array(quantizedVertexCount);
        var positions = new Array(quantizedVertexCount);
        var webMercatorTs = includeWebMercatorT ? new Array(quantizedVertexCount) : [];

        var minimum = scratchMinimum;
        minimum.x = Number.POSITIVE_INFINITY;
        minimum.y = Number.POSITIVE_INFINITY;
        minimum.z = Number.POSITIVE_INFINITY;

        var maximum = scratchMaximum;
        maximum.x = Number.NEGATIVE_INFINITY;
        maximum.y = Number.NEGATIVE_INFINITY;
        maximum.z = Number.NEGATIVE_INFINITY;

        var minLongitude = Number.POSITIVE_INFINITY;
        var maxLongitude = Number.NEGATIVE_INFINITY;
        var minLatitude = Number.POSITIVE_INFINITY;
        var maxLatitude = Number.NEGATIVE_INFINITY;

        for (var i = 0; i < quantizedVertexCount; ++i) {
            var rawU = uBuffer[i];
            var rawV = vBuffer[i];

            var u = rawU / maxShort;
            var v = rawV / maxShort;
            var height = _Math.CesiumMath.lerp(minimumHeight, maximumHeight, heightBuffer[i] / maxShort);

            cartographicScratch.longitude = _Math.CesiumMath.lerp(west, east, u);
            cartographicScratch.latitude = _Math.CesiumMath.lerp(south, north, v);
            cartographicScratch.height = height;

            minLongitude = Math.min(cartographicScratch.longitude, minLongitude);
            maxLongitude = Math.max(cartographicScratch.longitude, maxLongitude);
            minLatitude = Math.min(cartographicScratch.latitude, minLatitude);
            maxLatitude = Math.max(cartographicScratch.latitude, maxLatitude);

            var position = ellipsoid.cartographicToCartesian(cartographicScratch);

            uvs[i] = new Cartesian2.Cartesian2(u, v);
            heights[i] = height;
            positions[i] = position;

            if (includeWebMercatorT) {
                webMercatorTs[i] = (WebMercatorProjection.WebMercatorProjection.geodeticLatitudeToMercatorAngle(cartographicScratch.latitude) - southMercatorY) * oneOverMercatorHeight;
            }

            BoundingSphere.Matrix4.multiplyByPoint(toENU, position, cartesian3Scratch);

            Cartographic.Cartesian3.minimumByComponent(cartesian3Scratch, minimum, minimum);
            Cartographic.Cartesian3.maximumByComponent(cartesian3Scratch, maximum, maximum);
        }

        var westIndicesSouthToNorth = copyAndSort(parameters.westIndices, function(a, b) {
            return uvs[a].y - uvs[b].y;
        });
        var eastIndicesNorthToSouth = copyAndSort(parameters.eastIndices, function(a, b) {
            return uvs[b].y - uvs[a].y;
        });
        var southIndicesEastToWest = copyAndSort(parameters.southIndices, function(a, b) {
            return uvs[b].x - uvs[a].x;
        });
        var northIndicesWestToEast = copyAndSort(parameters.northIndices, function(a, b) {
            return uvs[a].x - uvs[b].x;
        });

        var orientedBoundingBox;
        var boundingSphere;

        // Bounding volumes need to be recomputed since the tile payload assumes no exaggeration.
        boundingSphere = BoundingSphere.BoundingSphere.fromPoints(positions);
        orientedBoundingBox = OrientedBoundingBox.OrientedBoundingBox.fromRectangle(rectangle, minimumHeight, maximumHeight, ellipsoid);

        var occludeePointInScaledSpace;
        if (exaggeration !== 1.0 || minimumHeight < 0.0) {
            // Horizon culling point needs to be recomputed since the tile payload assumes no exaggeration.
            var occluder = new TerrainEncoding.EllipsoidalOccluder(ellipsoid);
            occludeePointInScaledSpace = occluder.computeHorizonCullingPointPossiblyUnderEllipsoid(center, positions, minimumHeight);
        }

        var hMin = minimumHeight;
        hMin = Math.min(hMin, findMinMaxSkirts(parameters.westIndices, parameters.westSkirtHeight, heights, uvs, rectangle, ellipsoid, toENU, minimum, maximum));
        hMin = Math.min(hMin, findMinMaxSkirts(parameters.southIndices, parameters.southSkirtHeight, heights, uvs, rectangle, ellipsoid, toENU, minimum, maximum));
        hMin = Math.min(hMin, findMinMaxSkirts(parameters.eastIndices, parameters.eastSkirtHeight, heights, uvs, rectangle, ellipsoid, toENU, minimum, maximum));
        hMin = Math.min(hMin, findMinMaxSkirts(parameters.northIndices, parameters.northSkirtHeight, heights, uvs, rectangle, ellipsoid, toENU, minimum, maximum));

        var aaBox = new EllipsoidTangentPlane.AxisAlignedBoundingBox(minimum, maximum, center);
        var encoding = new TerrainEncoding.TerrainEncoding(aaBox, hMin, maximumHeight, fromENU, hasVertexNormals, includeWebMercatorT);
        var vertexStride = encoding.getStride();
        var size = quantizedVertexCount * vertexStride + edgeVertexCount * vertexStride;
        var vertexBuffer = new Float32Array(size);

        var bufferIndex = 0;
        for (var j = 0; j < quantizedVertexCount; ++j) {
            if (hasVertexNormals) {
                var n = j * 2.0;
                toPack.x = octEncodedNormals[n];
                toPack.y = octEncodedNormals[n + 1];

                if (exaggeration !== 1.0) {
                    var normal = AttributeCompression.AttributeCompression.octDecode(toPack.x, toPack.y, scratchNormal);
                    var fromENUNormal = Transforms.Transforms.eastNorthUpToFixedFrame(positions[j], ellipsoid, scratchFromENU);
                    var toENUNormal = BoundingSphere.Matrix4.inverseTransformation(fromENUNormal, scratchToENU);

                    BoundingSphere.Matrix4.multiplyByPointAsVector(toENUNormal, normal, normal);
                    normal.z *= exaggeration;
                    Cartographic.Cartesian3.normalize(normal, normal);

                    BoundingSphere.Matrix4.multiplyByPointAsVector(fromENUNormal, normal, normal);
                    Cartographic.Cartesian3.normalize(normal, normal);

                    AttributeCompression.AttributeCompression.octEncode(normal, toPack);
                }
            }

            bufferIndex = encoding.encode(vertexBuffer, bufferIndex, positions[j], uvs[j], heights[j], toPack, webMercatorTs[j]);
        }

        var edgeTriangleCount = Math.max(0, (edgeVertexCount - 4) * 2);
        var indexBufferLength = parameters.indices.length + edgeTriangleCount * 3;
        var indexBuffer = IndexDatatype.IndexDatatype.createTypedArray(quantizedVertexCount + edgeVertexCount, indexBufferLength);
        indexBuffer.set(parameters.indices, 0);

        var percentage = 0.0001;
        var lonOffset = (maxLongitude - minLongitude) * percentage;
        var latOffset = (maxLatitude - minLatitude) * percentage;
        var westLongitudeOffset = -lonOffset;
        var westLatitudeOffset = 0.0;
        var eastLongitudeOffset = lonOffset;
        var eastLatitudeOffset = 0.0;
        var northLongitudeOffset = 0.0;
        var northLatitudeOffset = latOffset;
        var southLongitudeOffset = 0.0;
        var southLatitudeOffset = -latOffset;

        // Add skirts.
        var vertexBufferIndex = quantizedVertexCount * vertexStride;
        addSkirt(vertexBuffer, vertexBufferIndex, westIndicesSouthToNorth, encoding, heights, uvs, octEncodedNormals, ellipsoid, rectangle, parameters.westSkirtHeight, exaggeration, southMercatorY, oneOverMercatorHeight, westLongitudeOffset, westLatitudeOffset);
        vertexBufferIndex += parameters.westIndices.length * vertexStride;
        addSkirt(vertexBuffer, vertexBufferIndex, southIndicesEastToWest, encoding, heights, uvs, octEncodedNormals, ellipsoid, rectangle, parameters.southSkirtHeight, exaggeration, southMercatorY, oneOverMercatorHeight, southLongitudeOffset, southLatitudeOffset);
        vertexBufferIndex += parameters.southIndices.length * vertexStride;
        addSkirt(vertexBuffer, vertexBufferIndex, eastIndicesNorthToSouth, encoding, heights, uvs, octEncodedNormals, ellipsoid, rectangle, parameters.eastSkirtHeight, exaggeration, southMercatorY, oneOverMercatorHeight, eastLongitudeOffset, eastLatitudeOffset);
        vertexBufferIndex += parameters.eastIndices.length * vertexStride;
        addSkirt(vertexBuffer, vertexBufferIndex, northIndicesWestToEast, encoding, heights, uvs, octEncodedNormals, ellipsoid, rectangle, parameters.northSkirtHeight, exaggeration, southMercatorY, oneOverMercatorHeight, northLongitudeOffset, northLatitudeOffset);

        var edgeMap = createEdgeMap(parameters.indices, uBuffer, vBuffer, parameters.level);
        TerrainProvider.addSkirtIndices(westIndicesSouthToNorth, southIndicesEastToWest, eastIndicesNorthToSouth, northIndicesWestToEast, quantizedVertexCount, indexBuffer, parameters.indices.length, edgeMap);

        transferableObjects.push(vertexBuffer.buffer, indexBuffer.buffer);

        return {
            vertices : vertexBuffer.buffer,
            indices : indexBuffer.buffer,
            westIndicesSouthToNorth : westIndicesSouthToNorth,
            southIndicesEastToWest : southIndicesEastToWest,
            eastIndicesNorthToSouth : eastIndicesNorthToSouth,
            northIndicesWestToEast : northIndicesWestToEast,
            vertexStride : vertexStride,
            center : center,
            minimumHeight : minimumHeight,
            maximumHeight : maximumHeight,
            boundingSphere : boundingSphere,
            orientedBoundingBox : orientedBoundingBox,
            occludeePointInScaledSpace : occludeePointInScaledSpace,
            encoding : encoding,
            indexCountWithoutSkirts : parameters.indices.length
        };
    }

    function createEdgeMap(indices, uBuffer, vBuffer, level) {
        if(level < 12){
            return undefined;
        }

        var edgeMap = {};
        var len = indices.length / 3;
        for(var i = 0;i < len;i += 3){
            var i0 = indices[i];
            var i1 = indices[i + 1];
            var i2 = indices[i + 2];
            if( (uBuffer[i0] === maxShort && uBuffer[i1] === maxShort) ||
                (uBuffer[i0] === 0 && uBuffer[i1] === 0) ||
                (vBuffer[i0] === maxShort && vBuffer[i1] === maxShort) ||
                (vBuffer[i0] === 0 && vBuffer[i1] === 0) ){
                edgeMap[i0 + '_' + i1] = 1;
                edgeMap[i1 + '_' + i0] = 1;
            }

            if( (uBuffer[i1] === maxShort && uBuffer[i2] === maxShort) ||
                (uBuffer[i1] === 0 && uBuffer[i2] === 0) ||
                (vBuffer[i1] === maxShort && vBuffer[i2] === maxShort) ||
                (vBuffer[i1] === 0 && vBuffer[i2] === 0) ){
                edgeMap[i1 + '_' + i2] = 1;
                edgeMap[i2 + '_' + i1] = 1;
            }

            if( (uBuffer[i2] === maxShort && uBuffer[i0] === maxShort) ||
                (uBuffer[i2] === 0 && uBuffer[i0] === 0) ||
                (vBuffer[i2] === maxShort && vBuffer[i0] === maxShort) ||
                (vBuffer[i2] === 0 && vBuffer[i0] === 0) ){
                edgeMap[i2 + '_' + i0] = 1;
                edgeMap[i0 + '_' + i2] = 1;
            }
        }

        return edgeMap;
    }

    function findMinMaxSkirts(edgeIndices, edgeHeight, heights, uvs, rectangle, ellipsoid, toENU, minimum, maximum) {
        var hMin = Number.POSITIVE_INFINITY;

        var north = rectangle.north;
        var south = rectangle.south;
        var east = rectangle.east;
        var west = rectangle.west;

        if (east < west) {
            east += _Math.CesiumMath.TWO_PI;
        }

        var length = edgeIndices.length;
        for (var i = 0; i < length; ++i) {
            var index = edgeIndices[i];
            var h = heights[index];
            var uv = uvs[index];

            cartographicScratch.longitude = _Math.CesiumMath.lerp(west, east, uv.x);
            cartographicScratch.latitude = _Math.CesiumMath.lerp(south, north, uv.y);
            cartographicScratch.height = h - edgeHeight;

            var position = ellipsoid.cartographicToCartesian(cartographicScratch, cartesian3Scratch);
            BoundingSphere.Matrix4.multiplyByPoint(toENU, position, position);

            Cartographic.Cartesian3.minimumByComponent(position, minimum, minimum);
            Cartographic.Cartesian3.maximumByComponent(position, maximum, maximum);

            hMin = Math.min(hMin, cartographicScratch.height);
        }
        return hMin;
    }

    function addSkirt(vertexBuffer, vertexBufferIndex, edgeVertices, encoding, heights, uvs, octEncodedNormals, ellipsoid, rectangle, skirtLength, exaggeration, southMercatorY, oneOverMercatorHeight, longitudeOffset, latitudeOffset) {
        var hasVertexNormals = when.defined(octEncodedNormals);

        var north = rectangle.north;
        var south = rectangle.south;
        var east = rectangle.east;
        var west = rectangle.west;

        if (east < west) {
            east += _Math.CesiumMath.TWO_PI;
        }

        var length = edgeVertices.length;
        for (var i = 0; i < length; ++i) {
            var index = edgeVertices[i];
            var h = heights[index];
            var uv = uvs[index];

            cartographicScratch.longitude = _Math.CesiumMath.lerp(west, east, uv.x) + longitudeOffset;
            cartographicScratch.latitude = _Math.CesiumMath.lerp(south, north, uv.y) + latitudeOffset;
            cartographicScratch.height = h - skirtLength;

            var position = ellipsoid.cartographicToCartesian(cartographicScratch, cartesian3Scratch);

            if (hasVertexNormals) {
                var n = index * 2.0;
                toPack.x = octEncodedNormals[n];
                toPack.y = octEncodedNormals[n + 1];

                if (exaggeration !== 1.0) {
                    var normal = AttributeCompression.AttributeCompression.octDecode(toPack.x, toPack.y, scratchNormal);
                    var fromENUNormal = Transforms.Transforms.eastNorthUpToFixedFrame(cartesian3Scratch, ellipsoid, scratchFromENU);
                    var toENUNormal = BoundingSphere.Matrix4.inverseTransformation(fromENUNormal, scratchToENU);

                    BoundingSphere.Matrix4.multiplyByPointAsVector(toENUNormal, normal, normal);
                    normal.z *= exaggeration;
                    Cartographic.Cartesian3.normalize(normal, normal);

                    BoundingSphere.Matrix4.multiplyByPointAsVector(fromENUNormal, normal, normal);
                    Cartographic.Cartesian3.normalize(normal, normal);

                    AttributeCompression.AttributeCompression.octEncode(normal, toPack);
                }
            }

            var webMercatorT;
            if (encoding.hasWebMercatorT) {
                webMercatorT = (WebMercatorProjection.WebMercatorProjection.geodeticLatitudeToMercatorAngle(cartographicScratch.latitude) - southMercatorY) * oneOverMercatorHeight;
            }

            vertexBufferIndex = encoding.encode(vertexBuffer, vertexBufferIndex, position, uv, cartographicScratch.height, toPack, webMercatorT);
        }
    }

    function copyAndSort(typedArray, comparator) {
        var copy;
        if (typeof typedArray.slice === 'function') {
            copy = typedArray.slice();
            if (typeof copy.sort !== 'function') {
                // Sliced typed array isn't sortable, so we can't use it.
                copy = undefined;
            }
        }

        if (!when.defined(copy)) {
            copy = Array.prototype.slice.call(typedArray);
        }

        copy.sort(comparator);

        return copy;
    }
    var createVerticesFromQuantizedTerrainMesh$1 = createTaskProcessorWorker(createVerticesFromQuantizedTerrainMesh);

    return createVerticesFromQuantizedTerrainMesh$1;

});
